Regenerative telegraph repeater



July 29, `1930. G. s'. VERNAM 1,771,453

REGENERATIVE TELEGRAPH REPEATER Filed June 9, 1928 24 ZZ E R 54.57 m WEST 5/ l 7 H 25 ql! E l- AVAVAVAVAV A'A-"A'A'A' i i I! s 5P T Y T' A TTHNEV Patented July 29, 193() UNITED STATES PATENT- ori-Ice GILBERT S; VERNIM, Ofi RIVER EDG-E, NEW JERSEY, ASSIGNOR TO AMERICAN TELE- vIIIEIOIil'll ANH TELEGRABE COMPANY, A CORPOBATON OF NEW YORK REGENERATLEVE TELEGRAPH REBATER Application le June 9, 1928. Serial No. 284,200.

rlhis invention `relates to telegraph systems, andparticularly to printing telegraph systems of the start-stop type.

An objectv of the invention is to regenerate int-o substantially their original form signals which. have been so badly distorted that further distortion would change their identity. v zy A feature oi' the invention is a rotary distributor, start-stop repeater theoretically capable of regenerating signals which have suifered distortion up to 50% of their normal length on eithery end. rdinar Y telegraph repeaters comprise one or more electromagnetic relaysA which, al-

device (commonlyr a condenser or -re-v lay) which is connected to the line through a distributor device for a short period at a time when the center of a signal is being received.

5;) The usual edect of line distortion is'to'cut ofi or eliminate the ends of signal impulses and therefore the middle portions of the signals are least Vadected. Since distortion may afeet either end oi a signal impulse, the great* y est possible freedom from the e'i`ects of distort-ion would be obtained in systems of the above type if an infinitely short receiving segmentwere used which would select onlythe very center of each signal impulse. Such 40 a system is not possible in practice because a segment of appreciable length is required to pass sutiicient current to actuat-e the signal responsive device. In accordance with this invention, signal impulses are applied directly to one winding though they increase the amplitude of the of a receiving relay without the use of a receiving segment, but the receiving relay is locked in whatever position it happens to be when thecenter of the signal should occur by means oi* a separate locking Winding energized through locking segments on the dis ,tributon Since the receiving relay repeats impulses" of characteristics dependentonly `on its position at the time the locking brush makes Contact with an associated segment, the degree of signal distortion permissible is not dependent on the minimum allowable widtlroi` the segment but only on the position ofthev edge of the segment, and may ap.- proach the maximum theoretical value, that is, on either end.

General `lascia/'priori of apparatusk A regenerative repeater system in accordance with this,` invention for repeating signals in either direction between two line sections,` one of which is, for convenience, called vloop east and the `other loop west, is illus are a locking relay, a sending relay, and a receiving relay, the relays associated with the loop west being identified as WLR, WSR and WRR., respectively, and thoselwith the loop east ELR, ESR, and ERR, respectively. The function of these relays will be made clearby a detailed description of the operation of the CII system in repeating signals from the loop west into the loop east.

Detailed description of operation Iany relay winding urges the relayrarmature from left to right, and viceversa when the electron flow is in the opposite direction.

The direction ofthe electron flow rom'the source at the distant end of the loop west is always from left to right-through the relay WRR as indicated-by the arrow. Thus the varmature of this relay is held on its right con- .tact by v.a loop current, which may conveniently .be made approximately 60 milliamperes. An opposing current of approximately 30 milliamperes flows through the lower winding, which will hereinafter be termed .the biasing winding. The circuit forV the 30 milliampere current extends from positive batterythrough the contact and armature oiV the west locking relayv WLR, through resist ance 11, throughfthe paralleled lower windings of the westlocking relay WLRand the west sending relay WSR, whichare shunted by aresistance 12, .and through the biasing winding of the receiving relay to ground. This locking current of 30 milliamperes holds the westlocking and' sending relays on their right contacts and tends. to move the v receiving relay armature to the left. The eiectve current in the windings of the locking and sending relays is small compared with that in the'lower winding Vof the receiving relay because of the shunting effect of resistance 12.

When the relays are all in their idlelcondition (on their right contacts) v the start magnet vcircuit for the west to east distrib-` utor is short-circuited. This circuit extends from negative battery through the right c0nv tact and armature of the west receiving relay WBB,'through the common rmg`19, locking brushLB, start segment?v of the locking,

distributor,ringsLD,through the start magnet 16 andback to 'negative batteryy through the .armature and rightvcontact of the east locking relay iELR.

Repeatingsgnals from 'west to east .In start-stoptelegraphy seven impulses are transmitted for each signal character. These comprise a ziirstor :starting impulse,A which is commonly a spacing impulse, followed byiive impulses which may be either marking or spacing and-represent the signal character to be transmitted. These are followed by a seventh or last marking impulse which stops the distributor and is termed the stop impulse. F or purposes of explanation it will be assumed that an F signal is to be repeated from the loop west into the loop east. The seven impulses ot an F signal are the start, which is spacing, #l marking, #2 spacing, #3 and :tf-4 marking, :#5 spacing and #6, the stop impulse, which is always a closed or marking impulse. Such a series of impulses is graphicallyrepresented at 20, the marking impulses being represented by'values above the Zero line and the spacing impulses as zero values of current. Thus the loop is normally closed but changes'to open or spacing condition at time A ywhen the start impulse is transmitted. f

This start or open impulse removes the 60 milliampere current from the upper winding of the west receiving relay VIRE and pervmits vthe 80 `milliampere biasing current in the lower winding to-move'the armature to the lett Contact. This applies positive battery to the start magnet .circuit which was previously traced and current iflows vfrom Vpositive battery'at the left Contact ofthe west receiving relay through the 'contact and armature of the relay, through the common ring19,`locking brush LB and start segment 7 Aof the locking distributor rings LD, through the start magnet 16 to negative battery at the right contact of the` east locking relay ELR. Start magnet 16 thereuponop erates to raise the lstop latch 17 and release the brush arm carrying the locking and sending brushes LB and SB.

Almost immediately after the locking brush leaves the start segment, thesending brush SB contacts with sending segment 7 which applies positive battery from segment v7 ,over sending brush SB, common ring 17, through resistances 22 and 23, the upper winding'of the east locking relay ELR and the upper winding of the east sending relay ESR to ground. An electron flow from right to left therefore occurs through the upper windingsot these two relays, overcomes the wea-k locking current and moves their armatures to their left contacts and opens the east loop at the east sendingrelay contacts. A 1;.

a resistance 26, through the biasing winding 2- of the east receiving relay ERR to ground. As in the case of the west locking and sending relays, resistance 26 may have such ya value as to limit the current in the lower windings of ELR 'and 'ESR to about y11 millou liamperes.V `ltmay be noted at this point that thecurrentin the lower or biasing winding of theeast receivingrelay ERR is now in such a` direction as to hold the armature on the right contact although the loop east circuit is open at the contacts ofthe eastsending relay. At this timeV the start magnet is deenergized, as its circuit has been opened by the locking brush LB passing oli the segment 7 Y Y Y The brushes traverse the segments in approximate synchronism with the signalA iinpulses` from the loop west so by the time the locking brush vLB reaches the #l segment oit the locking ring LD, the first impulse of the F signal, as vshown at 20, has been received, and the Vwest receiving relay armature is now on its right contact. When the locking brush makes-contact with #l segment ot the locking ring LD, it completes a circuit from negative battery at the right contact and armature of the west receiving relay WRR, through the common ring 19, brush LB and segment l of the locking distributor LD, through a y sistance 27 and thence to the left end ci the lower or biasing winding oit the west receiving relay WRR. The potential thus appliet through, resistance 27 to the left'end el' the biasing winding ofWRRis opposite in polarity and of higher potential than the potential previously applied to this point from positive battery through the right contact and armature of the West locking relay YVLR, resistance 11, the lower windings of WLR i, and WSR and resistance 12 in parallel. This change in potential causes a current of about 30 milliamperes to flow in the reverse direction through thebiasing winding oi the west receiving relay WRR which firmly loclrs the armature of the relay against its right contact. Regardless now of the electrical condition ofthe loop west` due to distortion in the received signal, the receiving relayarmature will remain on its marking contact as long as the locking brush is on segment #l and while the locking brush LB is still on segment #l the sending brush SB traverses its :#:1 segment. This completes a circuit trom the west receiving relay armature through contact #1, brush SB and common ring l? of the sending distributor rings SD, through resistances 22 and 23 and the upper windings of the east loclringrelay ELR and east sending relay ESR which moves the'` armatures of these relays to their rightormarling positions and sends a marking impulse into the loop east as shown at C in curve 30. It will be seen that an impulse of the correct polarity must be sent from the west'receiving relay WRR, through the east locking and` `sendingrelays ELR and ESR because the receiving relay armature is locked von its contact during the time the sending brush SB` is contacting with sending segment l of the sending distributor SD.

the looking brush LB .was on its #l segment,

as explained above, the receiving relay armature could not leave its rightormarking contact. Since thisV locking circuit is opened when the locking brush LB leaves segment #1, the west receiving relay l/VRR is thereafter under the control of the normal biasing current iiowiiigfrom vpositive battery at the right contact oi the west locking relay WLR through resistance ll and the lower windings of the relays 1i/VLR and WSR and theresistance l2 in parallel. Since there is` no current in the line winding at this time, the receiving relay armature is moved to its left ycontact by the normal 30 milliampere current from the above source in its lower or' biasing winding. r)The east locking and sending relays ELR and ESR remain on'their right contacts, however, as they are heldby the ll `milliainpere current in their locking windings,their operating windingsI being opened. at this time at the segments of the sending" distributor SD.

lhen the locking brush LB contacts with its #2 segment it once againcompletes the locking circuit from thearmature of the west receiving relay WRR to the left end of its biasing winding, and since the armatureV of relay lWRR is nou1 in its left or spacing position and therefore connected to positive battery, the current,appliedthrough resistance 27 has `the same [polarity as that :applied through the armature of the `west lockingi'elay VLR through resistance l1. Thenormal currentfoi' 80 milliampeies through the biasing winding 'ot WRR is therefore increased to` approximately 90 milliamperes, which holds the armature of the relay iirmlyagainst its left contact. it the loop west should close due to distortion whilethe locking brush LB is on the .#2 segment, 60` milliainperes will flow in the Operating winding of the west receiving relay tending to move its armature to its right Contact.` The armature will remain againstits leit Contact, however, due Vto the 90 milliamperes inthe biasing winding.

ln-the saine way as was previously described, the sending brush SB crosses thev l Hi" ies sending segment .#:2 w iile the locking brush LB is still on 'the .#2 locking segment. The correct impulse, (in this case a spacing impulse) is therefore sent from the west `receiving relay armature through the #Zsegment and brush'SB of the sending distributor SD to the operating-windings of the east sending andlocking relays, overcomingthell milliampere holding Vcurrent in the windings of those relays and movingtheir"armatures to the left or spacing contacts. The #2 impulse is thus repeated into the loop east at the armature and contact ofthe east 'sending relay `assume that nearly 50% of the first part of the #3 impulse has been wiped out and that nearly 50% of the .latter part of #4 impulse has also been eliminated, possibly by some fortuitous interference'on the lines.` Thus, instead of a marking impulse extending from time D to time F as shown in ycurve 20, we would have a much shorter marking Vimpulse as shown Vin curve 40 which begins a little less than half way between times D and E and ends only a little more than half way 'between times E and F, It will be remembered that the .distributor face is oriented with re- ,spect to the incoming signals so that the locking brushes LB just Contact with the edge of a segment on Vthe locking distributor LD as the exact center of an undistorted incoming impulse is being received. Thus referring to curve 20, it will be seen that the front edge of the #l segment on the locking distributor LD is ona line with thecenter-of the impulse received between timesy B7 and C. Therefore, the west receiving relay armature will be moved'to its marking Vcontact by the incoming distorted 1:3 impulse liust before the lockingbrush LB contacts with the #3 segment of the distributor LD. In contrast to this, it will be remembered that the #74:2 impulse had arrived in the receiving relay operating winding while the locking brush LB was still passing over the #l locking segment. Due to the assumption of nearly 50% distortion in the #3 signal impulse, however, this impulse does not appear in the receiving relay operating winding until the locking brush leaves #2 segment and is about to contact with #3 segment.V

Since the :#:8 impulse had moved the west receiving relay armature to the right or marking contact before the locking brush LB completed the locking circuit through the biasing winding of the relay, current of the correct polarity isapplied to the operated windings of the east locking and sending relays ELR and ESR and the :#:3 impulse is correctly repeated into loop east.V

While the locking brushv is still on locking esegment :#8 'the '#4 impulse (which is also marking as shown in curve 20) isreceivedin the operating winding of the receiving relay VRR. As stated above, it has-been assumed thatnearly 50% of the latter part of'the'itll impulse has been cut off by fortuitous `distortion but the locking brush LB makes contact with :rt/:4 locking segment just before the current in the loop west goes to zero, duetothe latter half of the fourth impulse being eliminated as shown in curve all).l The receiving relay armature, therefore, remains on its marking contact in spite of the distortion as the locking circuit to the biasing winding of the receiving relay was completed by the locking brush LB closing on segmentrfilbefore the receiving relay armature could move from its marking contact. Therefore, current of the correct polarity is applied to theoperating windings of the eastlocking and sending relays ELR and ESR when the sending brush SB makes contact with :#4 sending segment.

The #5 and #6 impulses are assumed to be perfect signa-ls and they will be repeated'in a normal way as were the .#1 and #2 impulses.

T he #6 impulse is always'a marking impulse and is used to stop the brushes and set the relays in their normalposition in preparation for the repeating of the neXt signal. The armature of the West .receiving relay TBR is moved to its right or marking contact and the sending brushes connect the marking current to the operating windings of the east locking and sending relays, thus closing the loop east and connecting negativebattery to the start magnet 16 at the armature and marking contact of the east locking relay ELR. The other end of the start magnet windingl is also connected to negative battery at the right or marking contact of the west receiving relay W RR through the locking brush LB and start segment 7 of the locking distributor LD. Therefore, the magnet does not operate untilthe next start impulse is received.

Reversing direction 0f transmission Heretofore it has been assumed that the loop east was closed at the distant station through a source of current applying about 60 milliamperes through the loop tothe operating winding of the east receiving relay ERR. This is the normal condition at the distant station while it is receiving. If while receiving, the distant operator wishes to signal the sending station, he opens the loop east. This opens the upper windingof the east receivingrelay ERB, leaving the latter under the control of its biasing winding. The normal biasing current of 30 milliamperes from the. right contact of the east locking relay ELB, throughresistance 25 and the lower windings of relay ELRand ESR and resistance 26 in parallel thereupon moves the armature of the east receiving relay ERR to its left contact. This completes acircuitafrom v lLlU vthe West to east distributor.

the left contact and armature of the east receiving relay ERR, through the common ring, locking brush,'start segment and start magnet of the east to West distributor to positive battery at the armature and right contact of the West locking relay WLR and `operates the start magnet on the east to vvest distributor in the same fashion outlined in detail above for y The east to West distributor brush will thereupon move over its associated segments, and, since the loop cast is open, repeats onlyl spacing impulses to the` West sending relay WSR which operates and holds the armature of thelatter relay in its left position and opensf the loop West.

\ After' completing one revolution, the'east to battery,"at the left' contacts of WLR andy Westbrushes remain stoppedbecause'each end of the start magnet is connected to negative ERR, respectively. When the West operator notes that the loop West is opened, he knovvs that the east `operator wishes to transmit to `him and he closes the loop West through his receiving apparatus. Transmission of signals from the loop east tothe. loop `vvest through the east to Westdistributor can then take place in the same manner as outlined in detail above in connection with transmission through the West to east distributor.

It should be noted that the armatures of the y West receiving relay WRR andwest locking relay WLR normally rest againstcontacts connected to battery of polarities opposite those of the contacts against Which the armatures of the east receiving relay ERR and east locking relay ELR normally lie. This makes possible the transmission through the repeater of a break signal from the receiving station as just described and prevents the distributor brushes from revolving continuously when a break signal is transmitted.

i Y. Summary the associated sending relay and supplies current of the requisite polarity lto lock the sending relay firmly on one contact or the other when the operating'vvinding of the sending frelay is not energized. It also controls the polarity of the .potentialv applied? tothe return side of the start magnet circuit and prevents the brush arm from revolving continuously during a break or open signal from the associated loop. A thirdl function is to control the polarity of the biasing cur-.3

rent in the'receiving relay and holdthe arma-V ture against its right or marking contact when an open or spacing signal is transmitted from the corresponding sending relay. The function of each pair of locking distributor rings is to'furnish a path for the start impulse from the armature ofthe associated receiving relay to the start magnet, and thereafter, during the repeating of signals, to lock the receiving relay at the centerl of each received signal impulse to prevent dis-j tortion in the incoming signals from being retransmitted.

The function of each pair of sending dis-` y tributor rings is to permit each Areceiving relay to control the opposite sending relay only While the receiving relay is locked in position by the locking distributor.' y i lt is to ybe particularly noted that a ,locking brushrshould. always be in contact with Y a locking .segment While the associated sending brush'is `passinglover a sending segment. In the system described it was foundconvenient to so orient the locking and sending segments that theV locking and y sending brushes left Vtheir segments substantially simultaneously. There would be no objection to moving the sending segments slightly Vto the left with respect to the locking seg ments but they should not be moved any farther to the right.

, Where, in the claims, it is specified that the sending brush leaves its associatedsegment before the locking brush, it isto be understood that the difference may be so slight that thebrushes leave their segmentssubstantially" simultaneously. Y y

What is claimed is: Y y 1. Ina telegraph system, a 'sourceof signal.`

impulses, distributing means, a receiving` re` lay and aregeiierating relay, said vreceiving relayv having an armature movable `between tvvo contacts connected to sources of current Vof opposite polarity, andhaving an. operating Winding connected to said source of signal impulses and a locking Winding connected through periodically closed contacts on said distributing meansto the armature of said receiving relay, a vvindingA on said regenerating, relay connected throughV a` `different set of, periodically closed Acontacts on said distributor to the armature ofsaid receiving` relay, said second contacts beingadapted to close later than said first contacts but to open before the opening of saidfirst contacts,

whereby said receiving relay armature is locked in position` during the time its armature is connected to the Winding'of the "re-` generating relay.

.2,V A systemas defined in claim l, char-` acterized in this, that said `distributor `means comprises arotary distributor in which thel first named contacts comprise acommon ring and a segmented ring and the second named contactscomprise a common ring and a seg mented ring With segments shorter than those ice of the iirst'named segmented ring, with brushes associating each common ring' with a segmented ring.

3. A system as defined in claim l, in which said regenerating relay has an additional locking winding and has an additional locking relay having an armature operable between two contacts connected to sources of current of opposite polarity and an operating winding and a locking winding, the operating winding being connected in circuit with the operating winding of said regenerating relay and the locking winding being connected in circuit with the locking winding on the regenerating relay, the armature of the locking relay and the sources of current connected to the contacts oi, the locking relay. 4. In a start-stop telegraph system 1n which a start impulse of fixed characteristicfollowedv by a plurality of impulsesof varying characteristics are transmitted, aregenerative repeater comprising a receiving relay having a line winding and a locking winding, an armature operable toa spacing position and a marking positionV and contacting 1n each position with one of two contacts connected to sources of potential of opposite polarity, a rotary distributor having a brush adapted to pass over a plurality of segments in succession, the irst of said segments being connected Vto-a source of current of oppositeV polarity to that of the marking vcontact of said receiving relay and the remaining segmentsbeing connectedrto the armature of said relay, means for restraining said brush, and current responsive means connected between the armature of the receiving relay and the other pole of said source of current connected to the spacing contact of said relay for releasing said vbrush restraining means, a repeating relay having an operating winding connected between said fbrush and the other terminals of saidsources of potential, a second brush on said distributor radapted to movein synchronism with the first brush and contact with a plurality ofsegmernts which are wider than said first segments, saidv second brush being connected to thearma-V ture of the receiving relay andthe seg-- ments'associated therewith being connected throughthe locking winding ofsaid relay to the other terminals of said sources of potential, said second brush and associated segments being so oriented with respect to re-A ceived impulses that the-brush makescontact with each segment at the time when the n center-of an undistorted signal isreceived,

and said first brush and associated segments being so oriented with respect to the second brush and segments thatcontact is made with each segment later than Athe time of initial contactbetweenthe second brush and a segment associated A therewith but during the time-"of Contact closure of the second brush.

5j In a half duplex, start-stop ltelegraph system, a `regenerative repeater comprising two groups of relays and twoV rotary distributors for repeating signals in each direction, a locking, a sending and a receiving relay in each of said groups and locking and sending segmented rings on each distributor, means comprising the locking and sending relay in each group for locking the receiving relay in that group when signals are being transmitted to the associated line section, means comprising the locking segments on one of said ydistributors for locking the receiving relay momentarily at the center of each received signal when signals are being received from the associated line section, means comprising the sending segments on said distributorv whereby said receiving relay controls the opposite sending relay during a portion of its locked period and means comprising the receiving and locking relay in each group for transmitting a break signal fromothe receivingsectioniof the line tothe transmitting section during transmission. Y Y

6. In atelegraph system, a'source of signal impulses of unit length, a receiving circuit for reception and storing of incoming signal .impulses and including a winding of a receiving relay, distributing means included in saidcircuithaving a series of long segments, locking means included insaid circuit adapted to cooperate with said long segments to X successive4 conditions in said circuit determined by the signal characterat the respective middle pointsot` the unit length signals, an operating vcircuit lincluding a regenerating'relay having locking means, and other distributing means having afseries of short .segmentsand adapted to causethe operation ofsaid regenerating relay in accordance with one of said fixed circuit'conditions, said distributing means having contacting means for their respective segments whereby the operating vcircuit will be closed and again opened ateach ofsaid short segments entirely within the time during which the receiving circuits is completed over va corresponding long segment. Y l

7; A, method of regenerating telegraph signals comprising storing incoming signals in accordance with the character of each signal at a moment during its greatest stability, then initiating regenerated impulses and then separately storing said impulses in accordance with the character of said stored signals, the storing of anincoming signal being maintained until the storing of the corre- Y sponding regenerated impulse has been fully separately storing a. regenerated impulse for retransmssionof a. character corresponding to the characterv of said stored signal, then discontinuing the storing of said stored signel7 discontinuing the storing of said regenerated impulse When the next regenerated impulse is initiated, and transmitting said Vregenerated impulse of unit length.

VIn testimony whereof, I have signed myV name to this specification this'8th day of June, 1928.

GILBERT S. VERNAM. 

